Concreate, Inc. delivers concrete polishing and custom staining for both commercial and residential projects primarily in Virginia and Maryland (but also up and down the East Coast). We work hand in hand with with designers, architects, project managers, general contractors, tradesmen, and home owners alike from start to finish. We welcome the opportunity to serve your polished concrete needs in every way possible.

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What Is a Durometer, and How Does It Apply to Concrete Floors?

What Is a Durometer, and How Does It Apply to Concrete Floors?

A concrete floor with control joints in an office building.

Durometer is a relative measurement of hardness you’ll typically use when selecting control joint fillers for your surfaces.

Key Takeaways:

  • Durometer gives a relative measurement of an object’s hardness
  • It isn’t an actual unit of measurement, but a comparison to other materials on the scale
  • Durometer is typically used to measure the hardness of a control joint filler
  • Selecting a joint filler with the correct durometer provides greater durability

Concrete is an incredibly durable material that will withstand all kinds of abuse. If you install concrete floors in your commercial building, you can expect them to last for decades as long as they’re correctly installed and maintained along the way. 

The installation process should involve putting in control joints, which are planned cracks in the surface that allow for movement caused by shrinkage and temperature changes. The control joints’ locations determine where the concrete will crack, giving you control over its final appearance. 

Applying joint filler to your control joints protects the joint edges and transfers floor load between your concrete slabs. The result is a more durable flooring solution.

Control joint fillers have evolved over the years, and modern contractors measure their hardness using durometer. What is a durometer? Here’s an answer to that question and information on why hardness matters when selecting a joint filler for your concrete floors.

A definition of durometer

Durometer is the relative measurement of a material’s hardness compared to other materials you measure using the same scale. So, it isn’t an actual measurement system but a comparative tool that gives you an idea of a material’s hardness. 

The scale ranges from zero to 100, with zero representing soft materials and 100 conveying incredibly hard objects or surfaces. When dealing with concrete, durometer is typically used to measure the hardness of control joint fillers, which are a vital part of the finished product. Your concrete joint fillers must be at least 80 on this scale, with the ideal hardness sitting between 80 and 85.

Control joint fillers of the past

Finding a control joint filler with the ideal durometer is critical because it helps create a more durable floor that will resist cracks. This durability is becoming more vital because forklifts and other heavy machinery are common in warehouse settings and can easily damage concrete floors if the joints don’t have an adequate seal.

When control joints were a new addition to the concrete flooring industry, technicians experimented with various soft and flexible materials. The primary purpose of these fillers was to keep debris out of the joints, so durability wasn’t a primary concern.

However, as tools like pallet jacks and forklifts became more widespread in warehouses and other businesses where concrete flooring was standard, the joint edges were exposed to more contact. This contact led to additional damage, so concrete professionals changed the joint fillers used.

Unfortunately, the industry went too far the other way by utilizing heavy-duty epoxy-based products as joint fillers. While these materials provided excellent joint edge protection, they welded the concrete slabs together, preventing movement as the concrete shrank and leading to stress cracking

How the technology evolved

Today, concrete experts have better materials at their disposal that do a more suitable job of protecting the joint edges without promoting cracking. Warehouses and other industrial centers are open 24 hours per day, and their floors are under incredible pressure, so durable joint fillers with the correct durometer rating are essential to stand up to the constant hard-wheeled traffic in these buildings.

Modern joint fillers have a different job, too, as they’re responsible for allowing wheel loads to transfer from one slab to another and no longer act like a sealant or caulk like the earliest products. These fillers must also maintain the flexibility that prevents the slabs from welding together and cracking. 

The design of these modern joint fillers is a little different. These products will tear if the joint movement exceeds their capability, and that’s by design. Rather than damaging the concrete, the filler will separate from it, making an easier repair when the time comes. 

Joint filler types

There are a couple of joint filler types to choose from, depending on your project. Both materials have advantages worth discussing as you make your decision.

Modern epoxy control joint fillers differ from earlier products because they’re semi-rigid and provide flexibility. These fillers sit between 80 and 85 on the durometer hardness scale, making them ideal for this purpose. 

When mixed correctly, epoxy joint fillers pour smoothly, and you can manually apply them with a bulk gun. You’ll then wait for the material to dry, which typically takes a day, and shave the joints down to make them even with the floor.

The other option is polyurea, which also offers an 80–85 durometer, so it’s rigid yet flexible enough to prevent the slabs from welding together and cracking. Polyurea is also more resistant to tearing than epoxy because of its higher elongation. 

Another benefit of polyurea is the speed at which it sets, as you can shave it down and open the floors to traffic within about half an hour. This speed makes it ideal in industrial settings where time is always of the essence. 

Completing your concrete floor

Understanding how durometer applies to concrete floors will provide clarity if you hear this term on a job site. You should also remember that control joint fillers should be between 80 and 85 on the durometer scale, as this ensures they’re hard enough to withstand the rigors of an industrial setting while retaining the flexibility necessary to allow movement of your slabs to prevent cracking.

Concreate understands the importance of control joint fillers and why the correct durometer hardness is essential to the job. We can assist with your concrete flooring project while ensuring your control joints promote longevity. Contact us or visit thisisconcrete.com for more information on durometer and why it matters to your project.